1. Field of the Invention
The present invention relates to a key-switch device for use as various input devices of personal computers and word processors, etc., and in particular it relates to a key-switch device corresponding to miniaturization and reduction in thickness of notebook-size personal computers.
2. Description of the Related Art
Along with demands for reduction in size and miniaturization of the entire device, various key-switch devices have been proposed, in which a key-top is attached at the upper end of a pair of lever members crosswise linked together so as to change the angle between the pair of lever members link-crossing each other by moving the key-top up-and-down.
The type of conventional key-switch device will be described below with reference to FIGS. 26 to 29.
As shown in FIG. 26, the conventional key-switch device principally comprises a key-top 101, a holder member 130 disposed beneath the key-top 101, a guide-supporting member 106 for guiding and supporting the key-top 101 between an elevated position separated from the holder member 130 and a lowered position coming close to the holder member 130, and a rubber spring 131 arranged between the key-top 101 and the holder-member 130.
The key-top 101, as shown in FIGS. 26 and 27, is provided with a character (not shown) formed on the top surface thereof by printing, and a pair of rotational retainers 101a and a pair of slide-retainers 101b, which are respectively arranged on the back surface. The pair of rotational retainers 101a are provided with retaining slots 104 respectively formed thereon while the pair of slide-retainers 101b are provided with retaining slots 105 respectively formed thereon.
The guide-supporting member 106 is formed of two resin-made lever members 107 and 108. As shown in FIG. 28, one U-shaped lever member 107 comprises a pair of arms 107a and a base-end part 107b connecting one end of one arm 107a to that of the other arm 107a. The other end of each arm 107a is provided with a retainer pin 107d protruded therefrom, and the central part of each arm 107a is provided with a shaft 107c formed inside thereof to protrude therefrom.
The other lever member 108, as shown in FIG. 29, comprises a pair of arms 108a, a base-end part 108b connecting one end of one arm 108a to that of the other arm 108a, retainer pins 108d formed at the other end of each arm 108a, and a depressing shaft 110 for connecting inside central parts of the arms 108a together. The central part of each arm 108a is provided with a hole 108c formed outside thereof, and at one end of each arm 108a, a retainer pin 108e is formed to protrude from outside.
The holder member 130, as shown in FIGS. 26 and 27, is formed of a metallic flat plate and comprises a pair of fitting parts 126 and a pair of retainers 127, which are cut-up from the surface. In addition, on the top surface of the holder member 130, a metallic frame 132 having plural openings 132a is arranged, and the fitting parts 126 and the retainers 127 protrude upwardly from the openings 132a of the frame 132.
The base-end part 107b of the one lever member 107 is rotatably retained in the retaining slots 104 of the rotational retainers 101a while the retainer pins 107d are slidably retained to the fitting parts 126 of the holder member 130.
Also, the retainer pins 108d of the other lever member 108 are slidably retained in the retaining slots 105 of the slide-retainers 101b of the key-top 101, while the retainer pins 108e are rotatably retained in the retainers 127 of the holder member 130.
Next, assembling of the key-switch device will be described: a conductive film sheet (not shown) is placed on the holder member 130. In addition, the sheet has the rubber spring 131 bonded thereon in advance. From the sheet, the fitting parts 126 of the holder member 130 and the retainers 127 protrude upwardly through the openings 132a of the frame 132.
Next, the one lever member 107 and the other lever member 108 are crosswise combined together so that each shaft 107c is rotatably inserted into the hole 108c so as to complete the guide-supporting member 106. Then, while the retainer pins 108e of the lever member 108 are press-fitted into holes of the retainers 127 of the holder member 130, the retainer pins 107d are slidably retained in the fitting parts 126. At this time, the depressing shaft 110 is positioned on the rubber spring 131.
Next, the key-top 101 is prepared so as to elastically abut the retainer pins 108d of the lever member 108 by depressing them from an obliquely upper direction (upper right part of FIG. 26), and the retainer pins 108d of the lever member 108 are inserted into the retaining slots 105 of the key-top 101 by trial and error.
Furthermore, the key-top 101 is urged to an upper part (the base-end part 107b and the retainer pins 108d) of the lever members 107 and 108 from the upper part so as to snap the retaining slots 104 of the key-top 101 into the base-end part 107b of the lever member 107.
In such a manner, the key-switch device is completed.
Next, operation of the key-switch device will be described: referring to FIG. 26, when pushing down the key-top 101, the base-end part 107b of the one lever member 107 rotates within the retaining slots 104 of the rotational retainers 101a while the retainer pins 108d of the other lever member 108 slides within the retaining slots 105 of the slide-retainers 101b horizontally (the lateral direction in FIG. 26). Simultaneously, the base-end part 108b of the lever member 108 rotates within retaining holes of the retainers 127 of the holder member 130 while the retainer pins 107d of the lever member 107 slides within the fitting parts 126 for slidably retaining the pin horizontally (the lateral direction in FIG. 26).
As a result, a bearing A for mutually journaling the lever members 107 and 108 on bearings moves downwardly while the depressing shaft 110 pushes the rubber spring 131 down gradually so as to be buckled. Thereby, a movable contact (not shown) within the rubber spring 131 establishes a short circuit in a fixed-contact pattern (not shown) on the holder member 130 so as to perform a predetermined switching operation.
When the pushing-down of the key-top 101 is canceled, the bearing A of both the lever members 107 and 108 is pushed up due to an elastic restoring force of the rubber spring 131 so as to perform the reverse operation (switching-off operation) to that mentioned above, resulting in returning the key-top 101 to the original position.
As mentioned above, various different characters or symbols may be printed on the key-tops 101 attached to the lever members 107 and 108.
A number of problems exist with the conventional key-top thus described. For example, after the key-switch device is assembled in advance, it may need to be changed to that of a different kind according to demand during assembling or after assembling. When removing the key-top 101 from the lever members 107 and 108, the key-top 101 has to be changed while maintaining the intersecting angle between the lever members 107 and 108. This is an extremely complicated operation unless a specially designed jig is used.
Another problem occurs when assembling the key-switch device: first, after assembling the guide-supporting member 106, in which the lever members 107 and 108 are crossed with each other, both the retainer pins 108e and 108e of the lever member 108 are press-fitted into the retainers 127 of the holder member 130.
Then, the retainer pins 107d and 107d of the one lever member 107 are inserted into both the fitting parts 126 and 126 so as to assemble the lever members 107 and 108 into the holder member 130. However, since the slender resin lever member 107 is liable to deflect, the retainer pins 107d and 107d sliding on the surface of the holder member 130 may simply come off the fitting parts 126 during the assembling.
In addition, also when operating as the key-switch device, the retainer pins 107d of the lever member 107 are slidably retained in the fitting parts 126; however, since each retainer pin 107d simply extends in the longitudinal direction, it may come off the fitting part 126 when sliding.
The rotational retainers 101a of the key-top 101 are snapped into the base-end part 107b of the lever member 107 via the retaining slots 104; however, since the lower snapping side of the rotational retainer 101a is open, there is a problem that the key-top 101 may simply come off the lever member 107 when an external force pushing up the key-top 101 is applied.
When the key-top 101 is assembled into the lever members 107 and 108, the key-top 101 is assembled in a state that the retaining slots 104 and the retaining slots 105 formed on the back side of the key-top 101 are downward oriented so that they cannot be visually confirmed, resulting in the complicated assembling operation.
Also, when the base-end part 108b of the lever member 108 is inserted and assembled into the retainers 127 of the holder member 130, there is a problem that the base-end part 108b cannot be smoothly inserted by catching on the sliding contact part of the retainers 127 into the base-end part 108b of the lever member 108 on the top surface of the holder member 130.